#define _CRT_SECURE_NO_WARNINGS 1
/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
	TreeNode* lowestCommonAncestor(TreeNode* root, TreeNode* p, TreeNode* q) {
		if (root == q || root == p || root == nullptr)  return root;

		TreeNode* left = lowestCommonAncestor(root->left, p, q);
		TreeNode* right = lowestCommonAncestor(root->right, p, q);

		if (left && right)
		{
			return root;
		}
		else if (left && !right)
		{
			return left;
		}
		else if (!left && right)
		{
			return right;
		}

		return nullptr;
	}
};